One of the hallmarks of aging is cellular senescence. Cells lose the ability to divide, differentiate, and replicate — yet stubbornly refuse to die.
These senescent cells not only lose function, but interfere with processes that create new cells when old ones die. They also harm nearby healthy cells by secreting pro-inflammatory factors and other tissue-damaging molecules.
Senescent cells don’t normally form before we’re past the age of 60, but they can arise in obese individuals and those with chronic diseases at a much earlier age. Whatever the reason you develop these “zombie cells” that refuse to die, they drive the aging process forward.
Lucky for all of us, answers are starting to emerge. . .
To stop senescent cells from gumming up our works, a class of compounds called senolytics has been developed in the last few years to selectively kill off senescent cells. Early animal testing has produced some remarkable results.
The latest study, published this July, has created a buzz.
A Drug Paired With a Nutrient
Professor James Kirkland, from the Mayo Clinic, led a team of 33 scientists to investigate the effect of a senolytic formula containing two strange bedfellows — the leukemia drug dasatinib and a natural flavonoid you’re probably familiar with, quercetin. Quercetin is a powerful antioxidant found in many fruits and vegetables like apple peel and onions.
The research team’s first test was to inject (transplant) a small number of senescent cells into young mice.
Two weeks later the mice experienced a slower walking speed, loss of muscle strength, less physical endurance and a reduction in daily activity. Levels fell by 20 to 50 per cent, imitating the function of elderly mice. The number of senescent cells also grew and spread into nearby tissues.
Dr. Kirkland said, “We wouldn’t believe it for a long time, so we did it again and again and again. It was weird to get this result with so few cells.”
Then the mice were given the senolytic.
After just three days, senescent cells were reduced in number and the decline in physical function slowed down.
Aging in Better Health With the Senolytic Duo
In the next test, middle-aged mice were supplemented with the senolytic on and off for four months. The result was healthier aging as seen in improvements in walking speed, endurance on a treadmill, grip strength and daily activity.
For their last test, very old mice received the senolytic supplement every other week. This led to a 36% increase in lifespan, and a one-third reduction in risk of death.
Commenting on the study, Aubrey de Grey, founder of the SENS Research Foundation on aging in Mountain View, California, had this to say:
“This is a very important result, and the deleterious effect of the transplanted cells is probably the best confirmation yet that senescent cells are actively toxic.
“More potent senolytic drugs are definitely coming, and I’m betting they’ll have a considerably greater effect.”
Richard J. Hodes, M.D., is Director of the National Institute on Aging, which provided most of the funding for the research. He says, “This study provides compelling evidence that targeting a fundamental aging process — in this case, cell senescence in mice — can delay age-related conditions, resulting in better health and longer life.”
Not Ready for Prime Time
According to the government’s MedlinePlus website, “Dasatinib is in a class of medications called kinase inhibitors. It works by blocking the action of an abnormal protein that signals cancer cells to multiply. This helps stop the spread of cancer cells.”
It apparently is not a chemotherapy drug as we commonly think of them but works by another mechanism.
As you can imagine, this drug for treating a certain type of leukemia is available only by prescription and comes with some extremely serious warnings of side effects.
The new senolytic combo has not been tested on humans nor is it known what doses will turn out to be appropriate and safe, assuming it works at all in us upright apes the way it does in mice. But the research is very promising and may lead to a new drive to target dangerous and damaging senescent cells.